Fan and Pad Evaporative Cooling
Fan and pad evaporative cooling is one of the most common cooling process used in greenhouses. The components of this process include a cellulose pad, overhead water supply tubing, a reservoir or gutter to collect excess water, a sump tank, a pump, piping and controls. These parts create a complete system that cools a greenhouse.
The process used in pad and fan cooling is similar to direct cooling. The first part of the process is making sure the pad is installed along a wall/side that is opposite the fans. The pad is soaked by the overhead water supply pipe. Once drenched, the pad has an air supply blown across it, and passed through exhaust fans. Unused water is collected below in a reservoir or gutter to the sump tank. The water returning to the tank is filtered, and re circulated to the top to redrench the water.
The pad-and-fan system contains many different variables in factoring how the system works. These can include pad size, water supply, sump capacity, controls, equipment, and coolers/chillers. Below is a description of each variable and ideas to keep in mind.
Pad Size– normally airflow rate is 8 cubic feet per minute per square foot
Can be modified for unshaded greenhouses
Airflow rate is total fan capacity needed and supplied to .1” of water static pressure
Height should be no less than 2’ and no greater than 8’
Water Supply- Make sure pads are not a solid wall of water
Differs upon cellulose of pad
Large system may need to require several pumps
Should be sized for 1 gallon/minute per 100 square feet of pad area
Sump Capacity – can be a tank or modular unit
Needs to be large enough to supply the pump
Controls– fan and pad system is activated at last stage of cooling
Controlled by a thermostat, controller or computer
Humidistat controls the humidity
Evaporative Cooling System- self-contained units
Usually mounted outside on wheels/walls and uses a hose and has an electrical connection
Placed near a door at end of greenhouse opposite the fans
Uses nozzles mounted outside of green house
Exhaust opening is used by the door, roof vent, or shutter to release warm air
Whaley Products
 Packaged Chillers Non-expandable (integrated pump tank) 1.5Ton – 20Ton Single / Dual Circuits Single / Dual Pumps |
 SAE Series Modular Chillers Expandable (pump & tank on separate skid) 1.5Ton – 200Ton Single / Dual Circuits |
 SAR Series Split Chillers Expandable (Outdoor Condensing Unit) (pump, tank, evaporator on indoor skid) 1.5Ton – 200Ton Single / Dual Circuits |